The farmers, some on tractors, surrounded sites run by major processors including Arla's centres in Ashby-de-la-Zouch in Leicestershire and Leeds, as well as the Robert Wiseman Dairy in Bridgwater, Somerset.

The demonstrations, organised by Farmers For Action (FFA), were a response to the latest 2p a litre cut in the price dairy farmers receive from milk processors.

The decrease means farmers will be paid 25p a litre for milk while the cost of production was 29p a litre, according to the National Farmers' Union dairy board.

Andrew Hemming, vice-chairman of FFA, said there were around 400 farmers in Leicestershire and up to 700 in Somerset. Others targeted a nearby Morrisons distribution depot.

"We've had a lot of support, not just from FFA members but a lot of other farmers too," he said.

"Government cannot and should not set prices but I will do everything in my power to get all levels of the supply chain to make the real changes needed to guarantee the industry's long-term future.

"Farmers and processors need to work together through an industry code of practice on contracts, and retailers have to help shift the focus away from short-term practices which are completely unsustainable."